This research program will investigate the role of the structural proteins, collagen and elastin, in cardiovascular calcification utilizing an experimental model of glutaraldehyde preserved porcine aortic valve (GPV) mineralization. Calcific degeneration of GPV bioprosthetic replacement valves represents a serious problem resulting in significant morbidity and mortality. Electron microscopy of pathological specimens of calcified GPV have shown that the principal morphological event occurring in this disease process is collagen fibril-oriented calcification. The possibility of elastin calcification occurring in GPV has not been addressed. Since the chief structural proteins present in GPV are collagen and elastin, the present study will focus on the biochemical and morphological events related to the experimental calcification of subcutaneous implants in rats of purified collagen and elastin preparations (both glutaraldehyde treated and nontreated) compared to GPV subcutaneous implantations. These experimental GPV calcific lesions resemble clinical GPV explants in terms of biochemical abnormalities and morphology both by light and electron microscopy. The working hypothesis of this proposal is that cardiovascular calcification, such as experimental GPV mineralization, occurs at least in part as a result of the calcification of the structural proteins collagen and elastin. To investigate this, the following will be pursued, utilizing a biochemical and morphologic approach: I. The collagen and elastin of GPV will be biochemically characterized from both unimplanted leaflets and after calcification has occurred. II. Subcutaneous implantations of purified collagen preparation (Types I, II, III) will be examined for calcification comparing both glutaraldehyde treated and untreated implants. III. Preparations of both aortic elastin and ear cartilage elastin, as well as elastin purified from GPV, will be studied as above (see II). IV. Biochemical structural modifications of collagen and elastin preparations as well as intact leaflets will be studied for their effect on the calcification.